1. Field of the Invention
This invention relates to a single lens reflex camera system which permits interchange of a finder unit, and more particularly to a camera system on which may be mounted an optical finder device provided with means capable of detecting the in-focus state of a picture-taking lens with respect to an object to be photographed.
2. Description of the Prior Art
In recent systematized single lens reflex cameras, the picture-taking lens structure as well as the structures from the finder structure to the back lid are designed as interchangeable units and, by interchanging respective units with other units having different functions, it is possible to create a camera system adaptable for a variety of purposes.
As a task which must necessarily be considered in designing such a systematized single lens reflex camera, there is a problem of the arrangement of interacting elements between a plurality of units forming the camera system. For example, the power source for supplying energy to the electrical devices of the camera system may be disposed in any unit by providing electrical connection between various units.
Particularly, in a camera system of such construction that the in-focus state of the picture-taking lens with respect to an object to be photographed is photoelectrically detected from part of an imaging light beam passed through the picture-taking lens and the lens system is driven to the in-focus position by an electric motor disposed in the picture-taking lens structure, a sufficient consideration must be given to the question of where it is most useful to dispose the power source for supplying power to the in-focus detecting device involving an electric circuit, the display device for displaying the in-focus state and the electric motor.